1. Field of the Invention
This invention starts from a process for monitoring and controlling an electric motor which is associated, through an adjusting device, with a movable object, especially one that is present on a motor vehicle.
2. Background Art
Such processes are intended to enable automatic adjustment of the movable object, which could be a window or a sunroof, for example, while taking into account safety requirements, which also follow from legal provisions, among other things. In particular, these safety requirements concern limiting the possible pinching force in case an object or body part is located in the closing path of the automatically closing window or sunroof.
The invention concerns especially such a process which involves producing a signal to stop or reverse the rotation of the motor as a function of a currently measured value of motor current and a value of motor current measured at a previous point in time.
Such a process is disclosed by DE 44 42 171 A1. This previously known process involves continuously capturing all the motor""s operating parameters xe2x80x94and thus in particular also the motor currentxe2x80x94at measurement time points which are equally spaced in time during the movement of the movable object. The operating parameters are used to determine an energy balance, and from that a total force, which in turn is used, with the help of a fixed time window, to determine a pinching force.
By contrast, this invention is based on the task of specifying a process which also reliably recognizes the case of pinching and is capable of stopping or reversing the window or sunroof in good time, however without this necessitating an elaborate calculation of energy balances, total forces, pinching forces, etc., as well as tracking the behavior of the force at equidistant measurement points over a time range comprising an entire closing process.
According to the invention this task is solved by storing in a memory the value of the motor current I(t0), which is always measured simultaneously with a specified slope (rising or falling) of a rectangular-pulse signal that is produced by a pulse generator and that is proportional to the motor speed, and using a stored value of the motor current I(txe2x88x92N), that was measured N(N greater than 1) relevant signal slopes ago, along with other parameters to form a reference value Iref, which is compared with the currently measured value of the motor current I(t0), and immediately producing the stopping or reversing signal if the currently measured value I(t0) exceeds the reference value Iref.
Alternatively, to make available another criterion for recognizing pinching, the currently measured value of the motor current I(t0) is compared with the value of the motor current I(txe2x88x921) that was measured and stored immediately before, and, if the currently measured value of the motor current I(t0) is greater than the value of the motor current stored immediately before I(txe2x88x921), a first counter xe2x80x9cgreaterxe2x80x9d is incremented by the value xe2x80x9conexe2x80x9d, and that, in order for the stopping or reversing signal to be produced, not only does the currently measured value I(t0) of the motor current have to exceed the reference value Iref, as described above, but in addition, the content of the xe2x80x9cgreaterxe2x80x9d counter must simultaneously exceed a threshold value sGr.